There can be no confidence that the “first marine” and “in situ” artefact scatters in the Dampier Archipelago, NW Australia are in their primary archaeological context.

The absence of known prehistoric underwater cultural heritage (UCH) sites on the inner continental shelf of Australia stands in stark contrast to the thousands of sites revealed elsewhere in the world. Two recent claims – Dortch et al. (D2019) and Benjamin et al. (B2020) – put forward the first in situ (i.e., primary context) marine UCH sites in the shallow waters of the Dampier Archipelago, NW Australia, each arguing the stone artefact scatters are at least 7000 years old and are now submerged because of post-glacial sea-level rise. From the data published in D2019 and B2020, we assess the explicit and implicit assumptions and uncertainties of these claims. We include new results of hydrodynamic modelling, new data on coastal erosion and new bathymetric data of northern Flying Foam Passage, leading to a reinterpretation of the archaeology and the sites' sedimentary settings.Whilst the presented lithic material of D2019 and B2020 clearly includes cultural artefacts, we find that the arguments for the sites being of primary context and reflecting early Holocene land surfaces do not stand up to scrutiny and that the available evidence is insufficient to establish the facts. In describing the assumptions and uncertainties in D2019 and B2020, we include example tests to help resolve them. On balance, it appears that these sites are intertidal, and many or all artefacts are likely to have been reworked. These and similar sites would benefit from a thorough appraisal of past and present coastal processes to produce a defensible understanding of site formation processes before it is possible to determine their true nature and significance, noting that, even as secondary sites, they would still inform our understanding of process and change. Such work would support more powerful contributions to submerged prehistory than attempts to seek the first, the earliest, the oldest or deepest.

BIOAVAILABLE AND TOTAL COPPER AND LEAD IN TERRIGENOUS SEDIMENTS IN THE INNER CONTINENTAL SHELF OFF VERACRUZ, SOUTHERN GULF OF MEXICO

The inner continental shelf adjacent to the city and port of Veracruz (ICSV) in the southern Gulf of Mexico, which is influenced by the Jamapa River, has been considered to be polluted. Moderate to high Cu and Pb concentrations have previously been reported in the shelf’s terrigenous sediments. These elements are derived from deposition of materials from mainland sources via river transport and may threaten marine life in the coastal area. Because Cu and Pb bioavailability has not been previously assessed in the region, the aim of this study was to determine (i) bioavailability and total concentrations of these elements in the terrigenous sediments of the ICSV, (ii) if concentrations of these elements in sediments are associated with distances from primary sources, and (iii) if concentrations differ during dry and rainy seasons. Bioavailable general average concentrations were 0.21 µg/g for Cu, and 0.24 µg/g for Pb, which accounted for 4.4-4.9 % of the total content. The bioavailable concentrations were higher during the rainy season, and in the fluvial plume of the Jamapa River. The total content of Cu and Pb was significantly associated with fine sediments and exhibited high concentrations in the new port facilities area. Hence, it is concluded that the Jamapa River is a primary source of trace metals to the ICSV. Finally, as concentrations of trace metals are lower than previous records for sediments in the southern Gulf of Mexico and lower than background levels and maximum permissible limits, the ICSV is presently not contaminated by Cu or Pb.

Saturation of the internal tide over the inner continental shelf. Part II: Parameterization

Here, we develop a framework for understanding the observations presented in the accompanying paper (Part I) by Becherer et al. (2021). In this framework, the internal tide saturates as it shoals due to amplitude limitation with decreasing water depth (H). From this framework evolves estimates of averaged energetics of the internal tide; specifically, energy, 〈APE〉, energy flux, 〈FE〉, and energy flux divergence, ∂x 〈FE〉. Since we observe that 〈D〉 ≈ ∂x 〈FE〉, we also interpret our estimate of ∂x 〈FE〉 as 〈D〉. These estimates represent a parameterization of the energy in the internal tide as it saturates over the inner continental shelf. The parameterization depends solely on depth-mean stratification and bathymetry. A summary result is that the cross-shelf depth dependencies of 〈APE〉, 〈FE〉 and ∂x 〈FE〉 are analogous to those for shoaling surface gravity waves in the surf zone, suggesting that the inner shelf is the surf zone for the internal tide. A test of our simple parameterization against a range of data sets suggests that it is broadly applicable.

Saturation of the internal tide over the inner continental shelf. Part I: Observations

Broadly-distributed measurements of velocity, density and turbulence spanning the inner shelf off central California indicate that (i) the average shoreward-directed internal tide energy flux (〈FE〉) decreases to near 0 at the 25 m isobath; (ii) the vertically-integrated turbulence dissipation rate (〈D〉) is approximately equal to the flux divergence of internal tide energy (∂x〈FE〉); (iii) the ratio of turbulence energy dissipation in the interior relative to the bottom boundary layer (BBL) decreases toward shallow waters; (iv) going inshore, 〈FE〉 becomes decorrelated with the incoming internal wave energy flux; and (v) 〈FE〉 becomes increasingly correlated with stratification toward shallower water.

ICHTHYOFAUNA IN THE INNER CONTINENTAL SHELF NEXT TO THE PARANAGUÁ ESTUARINE COMPLEX, SOUTHERN BRAZIL

The composition and structure of fish assemblages in the inner continental shelf of the Paraná State are affected by cold fronts and the rainfall regime. Data from fishing activities in this region, as well as the analysis of environmental characteristics, are the main tools available for understanding fish dynamics, under influence of increasing human activities. In order to better understand patterns and temporal variations in fish assemblages in the inner continental shelf of the Paraná State, a total of 24 double trawls were performed with an otter trawl between August 2000 and July 2001, in two sampling areas, the North area in front of the northern mouth of the Paranaguá Estuary Complex, and the South area, in front of the Leste beach. A total of 45,277 fish specimens belonging to 35 families and 97 species were caught. Sciaenidae was the most abundant family, with 37.1% of the total number of individuals caught, and with the highest richness (18 species). Statistical analyses evidenced significant differences in environmental characteristics and in fish fauna, and that both areas disturbances were observed in the fish assemblages during the dry and wet season, being more intense in the Southern area, disturbances that would be related to the shrimp fishing present in the two areas sampled in this study.

Observations of nonlinear momentum fluxes over the inner continental shelf

Nonlinear momentum fluxes over the inner continental shelf are examined using moored observations from multiple years at two different locations in the Middle Atlantic Bight. Inner shelf dynamics are often described in terms of a linear alongshore momentum balance, dominated by frictional stresses generated at the surface and bottom. In this study, observations over the North Carolina inner shelf show that the divergence of the cross-shelf flux of alongshore momentum is often substantial relative to the wind stress during periods of strong stratification. During upwelling at this location, offshore fluxes of alongshore momentum in the surface layer partially balance the wind stress and reduce the role of the bottom stress. During downwelling, onshore fluxes of alongshore momentum reinforce the wind stress and increase the role of bottom stress. Over the New England inner shelf, nonlinear terms have less of an impact in the momentum balance and exhibit different relationships with the wind forcing. Differences between locations and time periods are explained by variations in bottom slope, latitude, vertical shear and cross-shelf exchange. Over the New England inner shelf, where moored density data are available, variations in vertical shear are explained by a combination of thermal wind balance and wind stress. An implication of this study is that cross-shelf winds can potentially influence the alongshore momentum balance over the inner shelf, in contrast with deeper locations over the middle to outer shelf.

A new pinnotherid crab of the genus Pinnixulala Palacios Theil, Cuesta & Felder, 2016 from uncertain infaunal hosts in the northern Gulf of Mexico, with a rediagnosis and updated synonymy for the polychaete symbiont Pinnixulala retinens (Rathbun, 1918) (Decapoda: Brachyura: Pinnotheridae)

A new infaunal pinnotherid crab, Pinnixulala heardin. sp., is described from muddy substrates of the middle to inner continental shelf of the northern Gulf of Mexico. Molecular genetic analysis supports its separation from P. retinens (Rathbun, 1918), the only other western Atlantic member of the genus and a species most commonly found living as a symbiont of large polychaete worms. Both western Atlantic species are clearly separated from several described and undescribed populations of congeners occurring along shorelines of the eastern Pacific. We herein include a rediagnosis of P. retinens to facilitate morphological comparisons with P. heardin. sp. Unlike P. retinens, which is more common in shallow inshore waters and reaches larger sizes, the new species lacks development of a strong distally directed spine on the fourth pereopod ischium and has chelae that are at least as heavily developed as the second and third pereopods. In addition, the mature male first gonopods in P. heardin. sp. are tapered over their terminal one-third and directed distally, rather than being curved in their terminal one-third with the tips directed mesially, as they are in P. retinens. The new species is invariably collected from samples including infaunal worms and other invertebrates, but the specific hosts remain to be determined